Last Sat night my light just flickered and was pink in color. Sunday I put a rag on the photo cell and it came on normal and worked untill tonight, same think pinkish and flicker. the bulb is about a year old the rest is about 25 years old. What could it be? ballast, photo cell or bulb?

In the USA, complete mercury vapor fixtures are no longer made. Some parts may be available. Junk it and get a more efficient replacement. The only advantage of the mercury vapor is long lamp life. The ballast consumes more power than does the lamp-- very much an energy hog. High pressure sodium and metal halide are much more efficient and will save their purchase price in electricity savings over the MV in just a few months. The metal halide is often used at sports stadiums. The MV lamp dims gradually with use, rarely ever actually burning out. As it dims, the power used by the lamp actually increases. Eventually the lamp will become so dim that it can be seen only in a very dark location. If the yellow color is not a problem, get the high pressure sodium.

After many years of keeping my old MV light going, I went another route when the bulbs went up to around $20, . I bought a new fixture and bulb at Lowe's for a little more than $20. The new bulb was fl square tube with a standard base. The problem with it was after a year of two it burned out and was n/a anymore. At the suggestion of the electric guru at Lowes, I went the largest cfl that they had. It has been working for two years or so and gives out more light than any of other ones. Because the bulb is shielded from the weather with the large plastic globe it has not failed it. I am certain that it is the most efficient bulb of all the others.

We make a living by what we get, but we make a life by what we give......Winston Churchill

Please do let us know how the new fluorescent works for you. I have no experience with that particular lamp. Specifications for one lamp of the type indicate total lumens at about 4000. The MV when new was about 6300 lumens, so the fluorescent probably will not light the area as well. But the MV probably had degraded somewhat in output. The fluorescent is about 61 lumens per watt.

Your MV was probably 175 watts. The ballast for the MV typically uses over 500 watts, so the ballast uses more power than does the lamp. Failed MV ballasts often look like they have been cremated. A 70 watt high pressure sodium produces about 90 lumens per watt while the MV is about 42- 48 lumens per watt. Your power bill may drop noticeably.

Bus Driver, do you happen to know the lumens per watt, for metal halide fixtures? A few years ago, I ran across a deal and bought 50 some brand new 100 watt metal halide fixtures. I have several of them mounted in my shop, they put out a lot of light for just 100watts. I like them a lot!

The MH range from 90 to 115 in initial lumens per watt. As far as I know, the out put degrades a little as the lamp ages-- I know of no lighting type that does not degrade with age. Interestingly, the incandescents vary a great deal in lumens per watt depending on lamp size and type. The now-obsolete 100 watt incandescent produces many more lumens per watt than does the still-available (but not for long) 60 watt. I am by no means an expert. Some of these types I have never installed nor serviced. Some years ago, I attended a one-day seminar on lighting types. The technology has improved in some cases since then. Metal halide lamps have some tendency to explode when they fail. Fixtures designed to contain the fragments are desirable. Some of the lamps have an outer plastic casing for that purpose.

EDIT: Explode may be too strong a term, shatter might be better. But that can be hazardous as well.

I didn't know that about MH lamps exploding, thanks for that little tid bit of info! My fixtures are fully enclosed so that shouldn't be a problem. The fixtures I have are similar to those found under the canopy of a gas station, only smaller. The shipping labels indicated that they were headed to an electrical contractor for a Denny's restaurant project. I have no idea why they were not used, but it worked out quite well for me!

Gary, my church has MH recessed lights under an attached carport. They have the safety double wall globe for outdoor use. There is a prefix before the p/n so to tell them from the regular MH used inside. It is hard to tell the difference just by looking at the two of them.

We make a living by what we get, but we make a life by what we give......Winston Churchill